How is the Milky Way like a flag? Both can flutter from top to bottom. At least that’s the conclusion of a new study that will be published soon.

While tracking stars in the suburbs of our solar system, Mary Williams of the Leibniz Institute for Astrophysics in Potsdam, Germany, and more than two dozen team members found something unexpected. The stars seemed sway in and out along the galaxy’s north-south axis. They compared this movement to the fluttering of a flag.